DE10032370C1 - Carbon nanotube field effect transistor has two nanotubes spaced apart to prevent tunnel current between them - Google Patents

Abstract

The field effect transistor (100) has a first carbon nanotube (101), providing a source region, a channel region and a drain region and a second carbon nanotube (106), providing a gate region and supplied with a control voltage, for controlling the conductivity of the channel region. The nanotubes are spaced apart by a sufficient distance to prevent any tunnel current between them, e.g. the second nanotube is applied to an insulation layer (105) around the channel region provided by the first nanotube.

Description

The invention relates to a field effect transistor.

A large number are different from [1] Field effect transistors known.

An example of such a field effect transistor is so-called MOS field effect transistor.

According to today's technology, a MOS field-effect transistor still has a chip area of at least approximately 0.8 μm ² to 1.5 μm ² .

Furthermore, basics about so-called carbon nanotubes, hereinafter referred to as carbon nanotubes, known from [2] and [4].

A process for making carbon nanotubes by growing them on a substrate, is from [3] known.

Another method of making carbon Nanotubes by depositing the carbon nanotubes the gas phase is described in [4].

Furthermore, a method is known from [5] in which a electrically semiconducting carbon nanotube or one Metallically conductive carbon nanotube using doping of boron atoms and nitrogen atoms is converted into one Boron nitride nanotubes that have an electrically insulating effect.

Furthermore, a field effect transistor with a Carbon nanotube known to have two gold electrodes with each other electrically via a silicon dioxide substrate  controllably couples. In this case, the gold electrodes form the source area and the drain area of the Field effect transistor and the controlled channel area of the Field effect transistor is made of the carbon nanotube educated. About one below the silicon dioxide layer located silicon layer, which acts as the gate region of the Field effect transistor is used, the Channel-forming carbon nanotubes in their electrical properties, especially in their controlled electrical conductivity.

[7] also describes a method for producing a Silicon nanowire known.

The invention is therefore based on the problem of one Field effect transistor with a compared to the known Field effect transistors to specify less space.

A field effect transistor has a first nanotube, the a source area, a channel area and a drain Area of the field effect transistor forms. The first nanotube is a semi-conductive and / or a metallic conductive Nanotube. A second nanotube is also provided, which forms a gate region of the field effect transistor, the second nanotube being a semiconducting and / or a is metallic conductive nanotube. The first nanotube and the second nanotube are at a distance from each other arranged such that essentially no tunnel current between the nanotubes is possible and that by means of a Field effect by applying an electrical voltage to the second nanotube the conductivity of the channel area of the first nanotube is controllable.

Since the field effect transistor essentially consists of nanotubes a transistor is thus formed with respect to the known field effect transistors considerably less Land use created.  

Furthermore, a switching process between two states of the Field effect transistor with significantly reduced Power loss possible, especially due to the Compared to conventional field effect transistors considerably lower capacity and very good electrical Conductivity especially of carbon nanotubes.

The conductivity of the first nanotube is due to a local application of an electrical potential and thus of an electrical field, particularly in the Channel region forming section of the first nanotube varies, thereby reducing the functionality of a Field effect transistor has been created.

Any material can be used as material for the first nanotube can be used as long as the first nanotube is electrical semiconducting and / or metallically conductive properties having.

In addition, the source area or the drain area and the channel region of the first nanotube are doped. In this way, a potential barrier can be created in the channel area are generated to reduce leakage currents in the Leads to hibernation. Preferably, the source area and the drain region and the channel region are doped so that both between the source area and the channel area as a pn- also between the drain area and the channel area Transition or an np transition arises.

However, only the source area or the drain Region or the channel region can be doped.

To reduce leakage currents in the case of pn- Transitions or NP transitions also make sense, small area with a size of about 1 nm to about 5 nm  Nanotube between the p-doped region and the n- to leave the doped area undoped.

The invention can clearly be seen in that in a second near the channel region of the first nanotube Nanotube is arranged as a control element such that the conductivity of the first nanotube in the Channel forming part of the first nanotube can be controlled as required.

It should be noted that the two nanotubes are not touch, that means they are not in physical contact brought together, but by a dielectric, in simplest case by air, a gas or vacuum, separated from each other. Nevertheless, it must be ensured that the conductivity of the first by means of the field effect Nanotube can be influenced sufficiently.

Alternatively, the dielectric can also be inserted between the introduced into both nanotubes, electrically non-conductive Gas are formed.

The shortest distance between the first nanotube and the second, controlling nanotube is dependent on one maximum tolerable tunnel current between the two Nanotubes and the desired supply voltage with which the field effect transistor is selected. For example, with two carbon nanotubes, the second nanotube substantially perpendicular to the first Nanotube is arranged at a diameter of the two Nanotubes from 1 nm to 10 nm, the distance in one area to choose from 0.5 nm to 5 nm. The two are vivid In this case, nanotubes are arranged in a T-shape with respect to one another, see above that the field effect transistor has a T-shaped structure having.  

Furthermore, an insulator layer, d. H. a layer of electrically non-conductive material are used, for example made of an oxide material, e.g. B. made of silicon dioxide or of a nitride material, e.g. B. from Silicon nitride.

In this context, it is only necessary that essentially none between the two nanotubes Current flow is possible, a maximum of negligible Tunnel current.

The nanotubes can be semiconducting and / or metallic conductive carbon nanotubes.

Furthermore, single-walled and / or multi-walled nanotubes, in particular carbon nanotubes can be used.

The second nanotube can have three ends, one on End an electrical voltage can be applied and the two further ends are arranged such that of them due to the applied electrical voltage Conductivity of the channel area of the first nanotube can be changed.

This further training makes it possible to d. H. the active area where the conductivity changes can be increased, causing leakage currents occurring in the blocked state of the field effect transistor significantly be reduced.

According to a further embodiment of the invention, it is provided that the field effect transistor have two gates with which the field effect transistor switched, d. H. the conductivity in the channel area of the field effect transistor forming part of the first nanotube can be changed.  

This configuration eliminates the susceptibility to errors and Interference immunity improved.

In this case, a third nanotube is provided, the forms a second gate region of the field effect transistor, the third nanotube being a semiconducting and / or a is metallic conductive nanotube. The first nanotube and the third nanotube are at a distance from each other arranged in such a way that no tunnel current between the Nanotubes is possible and that by means of a field effect by applying an electrical voltage to the third Nanotube the conductivity of the channel area of the first Nanotube is controllable.

The second nanotube and the third nanotube can also be electrically coupled together.

In general, a predefinable number of others can in principle Carbon nanotubes on further insulator layers than further gates of the field effect transistor have grown up, whereby a simple logical OR arrangement by means of a Field effect transistor is created.

Furthermore, each nanotube can be made according to another Embodiment of the invention a plurality or even one Variety, clearly a whole bundle of individual nanotubes have, whereby the stability and reliability of the formed field effect transistor is further improved.

The ends of those used in the field effect transistor Nanotubes can optionally be open or closed.

Embodiments of the invention are in the figures shown and are explained in more detail below.

Show it  

Fig. 1 shows a cross section of a field effect transistor according to a first embodiment of the invention;

Fig. 2 is a cross section of a field effect transistor according to a second embodiment of the invention;

Fig. 3 is a cross section of a field effect transistor according to a third embodiment of the invention;

Fig. 4 is a cross section of a field effect transistor according to a fourth embodiment of the invention;

Fig. 5 is a cross section of a field effect transistor according to a fifth embodiment of the invention; and

Fig. 6 shows a cross section of a field effect transistor according to a sixth embodiment of the invention.

In the exemplary embodiments described below same elements of a field effect transistor with identical Reference numbers marked.

Fig. 1 shows a field-effect transistor 100 according to a first embodiment of the invention.

The field effect transistor 100 has an electrically semiconductive or metallically conductive first carbon nanotube 101 with a length of approximately up to 100 nm and a thickness of approximately 1 nm to 10 nm.

The first carbon nanotube 101 and all of the carbon nanotubes described below, including the carbon nanotubes of the further exemplary embodiments, are produced by means of a deposition process from the gas phase, as described in [2], or by means of growth, as described in [3] is made.

The first carbon nanotube 101 has a source region 102 , a channel region 103 and a drain region 104 of the field effect transistor 100 .

An insulator layer 105 made of silicon nitride or silicon dioxide is applied to the first carbon nanotube 101 in the channel region 103 by means of a CVD method or a sputtering method. The insulator layer 105 has a thickness of approximately 2 nm to 5 nm and a length that is at least as long as the length of the channel region 103 .

A second carbon nanotube 106 has grown on the insulator layer substantially perpendicular to the first carbon nanotube 101 in accordance with the method described in [y].

The second carbon nanotube 106 has a length of approximately 10 nm and a thickness of approximately 1 nm to 10 nm.

It should be noted in this connection that it is essentially irrelevant for the functionality how long or how thick a carbon nanotube 101 , 106 is. They can also differ significantly from one another.

Furthermore, the carbon nanotubes 101 , 106 can also have a curved, ie curved shape, as long as the functionality described above is ensured.

An electrical control voltage, the gate voltage, is applied to the second carbon nanotube 106 , which functions as the gate of the field effect transistor, as a result of which an electric field is generated. The electrical field is used to change the potential in the channel region 103 by means of a field effect and thus to control the electrical conductivity of the first carbon nanotube 101 .

Fig. 2 shows a field effect transistor 200 according to a second embodiment of the invention.

The field effect transistor 200 differs from the field effect transistor 100 according to the first exemplary embodiment essentially in that the first carbon nanotube 201 is formed by three carbon nanotubes 202 , 203 , 204 which are electrically conductively coupled to one another.

A first partial nanotube 202 , which forms the source region of the field effect transistor 200 , is a metallically conductive carbon nanotube.

A second partial nanotube 203 , which forms the channel region of the field effect transistor 200 , is a semiconducting carbon nanotube.

A third partial nanotube 204 , which forms the drain region of the field effect transistor 200 , is in turn a metallically conductive carbon nanotube.

According to the second exemplary embodiment, the second partial nanotube 203 is longer than the thickness of the second carbon nanotube 106 , ie in other words, the second partial nanotube 203 extends laterally beyond the diameter of the second carbon nanotube 106 .

Fig. 3 shows a field effect transistor 300 according to a third embodiment of the invention.

The field effect transistor 300 differs from the field effect transistor 200 according to the second exemplary embodiment essentially in that the second partial nanotube 203 is shorter than the thickness of the second carbon nanotube 106 , ie in other words, the second partial nanotube 203 is the extension of the channel region is laterally smaller than the diameter of the second carbon nanotube 106 .

In general, it should be noted that the longer the channel region, for example the second partial nanotube 203 , the lower the leakage currents within the blocked field effect transistor. On the other hand, the influence of the second carbon nanotube 106 , which forms the gate of the field effect transistor, is greater, the shorter the channel region, for example the second partial nanotube 203 .

Fig. 4 shows a field-effect transistor 400 according to a fourth embodiment of the invention.

The first carbon nanotube 401 of the field effect transistor 400 has a total of five partial nanotubes 402 , 403 , 404 , 405 , 406 .

A first partial nanotube 402 , which forms the source region of the field effect transistor 400 , is a metallically conductive carbon nanotube.

The channel region of the field effect transistor 400 is formed by the second partial nanotube 403 , the third partial nanotube 404 and the fourth partial nanotube 405 , the second partial nanotube 403 being a semiconducting, the third partial nanotube 404 being a metallically conductive and the fourth part nanotube 405 is again a semiconducting carbon nanotube.

The fifth partial nanotube 406 , which forms the drain region of the field effect transistor 400 , is in turn a metallically conductive carbon nanotube.

The channel area is thus generally formed by partial Nanotubes with one at each end of the channel area  semiconducting carbon nanotube is arranged and in between any number of metallically conductive and semiconducting carbon nanotubes.

According to this exemplary embodiment, the second carbon nanotube 407 is gamma-shaped, ie the second carbon nanotube 407 has two branches 408 , 409 , generally any number of branches, the branches 408 , 409 on the insulator layer 105 over the region of the arranged second part nanotube 403 and the fourth part nanotube 405 , whereby the channel region of the field effect transistor 400 can be easily expanded.

Fig. 5 shows a field-effect transistor 500 according to a fifth embodiment of the invention.

The field effect transistor 500 differs from the field effect transistor 300 according to the third exemplary embodiment essentially in that a second insulator layer 501 is applied to the first carbon nanotube in its channel region and a third carbon nanotube 502 is grown thereon.

The third carbon nanotube 502 is electrically coupled to the second carbon nanotube 106 , so that a field effect transistor 500 with multiple gates is clearly formed.

In general, a predefinable number of others can in principle Carbon nanotubes (not shown) on others Insulator layers or an insulator layer that is continuous is applied around the first carbon nanotube, grew up.

Fig. 6 shows a field effect transistor 600 according to a sixth embodiment of the invention.

The field effect transistor 600 differs from the field effect transistor 300 according to the third exemplary embodiment essentially in that the second carbon nanotube is formed by a large number, that is to say clearly a bundle, of carbon nanotubes 601 , which are used together as the gate of the field effect transistor 600 .

The following publications are cited in this document:
[1] U. Tietze, Ch. Schenk, semiconductor circuit technology, 11th edition, Springer Verlag, ISBN 3-540-64192-0, pp. 187-218, 1999.
[2] ZF Ren et al. Synthesis of Large Arrays of Well-Aligned Carbon Nanotubes on Glass, SIENCE, Volume 282 . Pp. 1105-1107, November 1998
[3] Young Sang Suh and Yin Seong Lee, Highly-Ordered Two-Dimensional Carbon-Nanotubes Areas, Applied Physics Letters, Volume 75 , No. 14, pp. 2047-2049, October 1991
[4] T. Dekker, Carbon-Nanotubes as Molecular Quantum Wires, Physics Today, pp. 22-28, May 1999
[5] W. Han et al. Synthesis of Boron Nitride Nanotubes From Carbon Nanotubes by a substitution Reaction, Applied Physics Letters, Volume 73 , Number 21 , pp. 3085-3087, November 1998
[6] R. Martel et al. Single- and Multi-Wall Carbon Nanotube Field-Effect Transistors, Applied Physics Letters, Volume 73 , Number 17 , pp. 2447-2449, October 1998
[7] Sung-Wook Chung et al. Silicon nanowire devices, Applied Physics Letters, Vol. 76, No. 15, pp. 2068-2070, 1999

Reference list

100

Field effect transistor

101

First carbon nanotube

102

Source area

103

Channel area

104

Drain area

105

Insulator layer

106

Second carbon nanotube

200

Field effect transistor

201

First carbon nanotube

202

First partial nanotube

203

Second part nanotube

204

Third part nanotube

300

Field effect transistor

400

Field effect transistor

401

First carbon nanotube

402

First partial nanotube

403

Second part nanotube

404

Third part nanotube

405

Fourth part nanotube

406

Fifth partial nanotube

407

Second carbon nanotube

408

branch

409

branch

500

Field effect transistor

501

Second insulator layer

502

Third carbon nanotube

600

Field effect transistor

601

Bundle of carbon nanotubes

Claims (10)

1. Field effect transistor, with
a first nanotube, which forms a source region, a channel region and a drain region of the field effect transistor, the first nanotube being a semiconducting and / or a metallically conducting nanotube,
a second nanotube, which forms a gate region of the field effect transistor, the second nanotube being a semiconducting and / or a metallically conducting nanotube, and
the first nanotube and the second nanotube being arranged at a distance from one another such that essentially no tunnel current is possible between the nanotubes and that the conductivity of the channel region of the first nanotube can be controlled by means of a field effect by applying an electrical voltage to the second nanotube. 2. Field effect transistor according to claim 1, in which the first nanotube and / or the second nanotube is a carbon nanotube. 3. Field effect transistor according to claim 1 or 2, which is electrically non-conductive between the nanotubes Gas is introduced. 4. Field effect transistor according to one of claims 1 to 3, in which the first nanotube and / or the second nanotube has multiple walls. 5. Field effect transistor according to one of claims 1 to 4,
in which an insulator layer is applied at least on the channel region of the first nanotube, and
in which the second nanotube is applied to the insulator layer. 6. field effect transistor according to claim 5, in which the insulator layer is an oxide material or a Contains nitride material. 7. field effect transistor according to one of claims 1 to 6, in which the second nanotube has three ends, where on one end an electrical voltage can be applied and the two other ends are arranged such that of them due to the applied electrical voltage Conductivity of the channel area of the first nanotube can be changed. 8. field effect transistor according to one of claims 1 to 7,
in which a third nanotube is provided, which forms a second gate region of the field effect transistor, the third nanotube being a semiconducting and / or a metallically conducting nanotube, and
wherein the first nanotube and the third nanotube are arranged at a distance from one another such that no tunnel current is possible between the nanotubes and that the conductivity of the channel region of the first nanotube can be controlled by means of a field effect by applying an electrical voltage to the third nanotube. 9. field effect transistor according to one of claims 1 to 8, where the second nanotube and the third nanotube are electrically coupled together. 10. field effect transistor according to one of claims 1 to 9, in which at least one of the nanotubes has a multiplicity of Has nanotubes.